T-reg: A High-Voltage Regulator for Tube Amps

Tube amplifiers can benefit from regulated and stabilized power supplies, especially sensitive preamplifier stages, but also (single-ended) power amps. But traditional high-voltage regulators add several extra tubes, complexity, and power losses, while good performance is not easy to obtain. This article, published in audioXpress, April 2009, describes a novel design that is very simple yet offers excellent performance. Output voltage is fully adjustable with a single resistor without any compromises in performance.

Ethan Winer explains how to "Build the Mojo Maestro," a simple device that allows "subtle distortion" or saturation from any recording or track. Just using two diodes and a few resistors, Winer designed this simple box using the free LTspice simulation software and only half a dozen parts. And the results can be heard on the audioXpress website, with Winer playing multiple instruments, with and without the "Mojo effect." This article was originally published in audioXpress, October 2017.

Keeping things small and inexpensive — and at the beginner’s level — Rick Spencer shows you how to build your own single-ended amp. For about $10 worth of tubes and some small transformers, you can build this neat little amp in one weekend. This article was originally published in audioXpress, April 2004.

In this classical tube amplifier project, author Bob McIntyre offers what is effectively the foundation for many designs that we can find currently in the market. This is not surprising. The Mighty Mouse is indeed a good sounding and inexpensive project that is also a good introduction to tube amplification. This article was originally published in audioXpress, April 2006.

In this article for audioXpress, Bill Reeve discusses “An Alternative to Linear Regulators.” A project were he searches for equivalent power-line ripple rejection with less power dissipation, using a source follower-based (SFB) low-pass filter. Because no one wants to listen to an audio amplifier that hums. This article was originally published in audioXpress, April 2014.

Antique tube radios are some of the most coveted vintage electronics any audio enthusiast can acquire. They sound absolutely great, both as for what they are intended - to work as a good old analog radio - but also as an amplifier for external audio sources, including any digital source. In this audioXpress article, from May 2012, Bill Reeve shares how to approach such projects and provides excellent advice.

Accurately setting the bias level for push-pull output stages is important to maximize amplifier performance and tube life. This circuit measures error relative to the target bias current and error relative to a balanced condition in the push-pull pair. The meter is compact, low-cost, simple, and accurate thanks to the use of a window comparator IC - a Linear Technology LTC1042. This article was originally published in audioXpress, July 2012.

In this high quality project, Robert Nance Dee designs a potentiometer for accuracy and flexibility. A pot with 64 levels and precision metal film resistors that is hard to beat for sound or facility, as he describes it. The project started with a clean sheet, looking to address potentiometer design with a quality that rivaled existing designs while maintaining a reasonable cost. This article was originally published in audioXpress, September 2011.

Published in two separate parts in audioXpress October and November 2007, this hybrid amp design is a detailed and interesting project, frequently referenced by other DIY audio enthusiasts. We thought it was time to make it available online in its entirety, in the best possible quality. The article discusses the unity-gain, single-ended MOSFET output stage, the valve voltage amplification stage and wraps up with the power supplies, printed circuit boards, and construction.

Simon Brown rethinks what he needs as the amp that will be the centerpiece in his own audio system and perfects a previous design with a true hybrid design. As he writes, "This amp is a “hybrid” in many ways. There is the obvious way in which it uses both valves and MOSFETs. But it’s also a hybrid in its use of enriched Class A/B, which means it is running Class A up to a few watts. This is deliberate." Read the complete project now. This article was originally published in audioXpress, March 2007.